How delightfully appropriate that a film about the invention of the vibrator should induce curled toes, reddened faces and the odd blasphemous outburst. Tanya Wexler’s staggeringly bad period comedy wears out its AA batteries fast, despite its teasing premise.

We are in London, 1880, and female patients are lining up around the block to experience pelvic massage at the hands of doctor Mortimer Granville (Hugh Dancy). Our hero needs a device to save his cramping fingers, so he and a wealthy chum (Rupert Everett, both stupefied and stupefying) adapt an electric feather duster to do the same job, but faster.

Meanwhile, Maggie Gyllenhaal’s feminist firebrand-stroke-love interest Charlotte flaps through every scene like a pigeon in an attic, plopping social context on the heads of everyone below. “By the time I’m gone, women will have the vote, equal education and rights over their own bodies!” she chirps, with uncanny foresight. (In fact, the entire cast turn out to be sages: “Imagine if everyone had one of these!” moos Everett as he fiddles with a prototype telephone.)

As two of Granville’s patients, Sheridan Smith and Anna Chancellor gamely sigh, honk and whoop their way to orgasm. The pleasure, I am sorry to report, is all theirs.